The cardiopulmonary and acid-base effects of butorphanol in desflurane anesthetized dogs breathing spontaneously were evaluated.

To this 20 adult healthy, male and female dogs were used. They were separated into two groups of 10 animals each (GS and GB). Anesthesia was induced with propofol (8.4±0.8 mg/kg IV) and maintained with desflurane (10V %). After 40 minutes of induction, the animals from GS received saline solution at 0.9% (0.05 mL/kg) and from GB received butorphanol (0.4 mg/kg), both applied intramuscularly. Heart (HR) and respiratory (RR) rates; systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures; arterial blood pH (pH), arterial partial pressure of O₂ (PaO₂) and CO₂ (PaCO₂); base deficit (BD), arterial oxygen saturation (SaO₂) and bicarbonate ion concentration (HCO₃) were measured. The measurements were taken immediately before the application of the agents (M0). Serial measurements were carried out at 15 minutes intervals after the administration of butorphanol or saline up to 75 minutes (M15, M30, M45, M60 and M75). Data were evaluated by analysis of variance for repeated measures (ANOVA), followed by the Tukey test (p<0.05).

After butorphanol administration SAP (from 115 ± 11 to 91 ± 12 mmHg; p<0.05), DAP (from 67 ± 10 to 47 ± 8 mmHg; p<0.05) and MAP (from 86 ± 10 to 64 ± 10 mmHg; p<0.05) decreased significantly. PaO₂ had discreet alterations, however without clinical meaning. RR (from 11 ± 3 to 8 ± 3 mpm; p<0.05) and pH (from 7.28 ± 0.05 to 7.25 ± 0.05; p<0.05) decreased after butorphanol administration while PaCO₂ increased significantly (from 49.9 ± 5 to 58.5 ± 6 mmHg; p<0.05).

It was possible to conclude that butorphanol administration in desflurane anesthetized dogs produced reduction in the averages of the systolic, diastolic and mean arterial pressure and relatively to the respiratory parameters, the opioid produced respiratory depression in spontaneously breathing dogs.